As per my knowledge, the oldest reference to the word Hinduism comes from the Prithviraj Raso, a historiacalhistorical romance attributed to Chanda Bardai where the word Hindus and Turks can be senseen for the first time in certain versions of it. In "Geeta" as well, there is no reference to the word Hinduism. Instead, "Sanatana Dharma" has been used there. So, there is no clear reference to it being a religion but there are references of it being ethno-geographical. It has been used by Persians to differentiate themselves from the people living beyond Indus river. So, it has been a source of great debate for a long time as to Who Inventedwho invented Hinduism. Britishers claim its invention and costructionconstruction after 18th century AD but the topic is still highly debatable.